This invention relates to an apparatus and method for evaluating the characteristics of an object and, in particular, to a method and apparatus for evaluating object defects utilizing computer processing techniques.
In present day manufacturing, it is often necessary to examine a product to assess whether the characteristics of the product deviate from desired or ideal characteristics. These deviations can be characterized as defects and when the defects either individually or as a composite exceed certain levels the product may be rejected.
A particular example of this type of evaluation is in the manufacture of printed circuit boards and specifically in evaluating the characteristics of the solder joints used on such boards. In solder joint inspection, the solder joints are examined for a variety of defects ranging from the overall joint shape to local abnormalities such as peaks or holes which might be in the range of 0.001" to 0.002" in size.
In order to be able to resolve solder joint defects of this small size and to also be able to cover the entire range of defect types, some 10,000 data points of each joint may have to be evaluated. In conventional processing of this data with standard image recognition techniques, the presence or absence of all defects of interest would be sequentially identified, one by one. However, following this procedure with such a large number of data points would be very time consuming. In particular, it has been experimentally determined that when using this processing to evaluate a surface mount solder joint for a flat pack, the processing time takes as much as a minute or more.
In high volume production, this amount of processing time per solder joint is intolerably high. As a result, a processing procedure which significantly reduces this time would be highly desirable.
It is therefore, an object of the present invention to provide an improved method and apparatus for evaluating the defects in an object.
It is a further object of the present invention to provide an improved method and apparatus for evaluating the defects in solder joints.
It is yet a further object of the present invention to provide a method and apparatus for evaluating the defects in an object and, in particular, a solder joint, in a reduced amount of time.